Bit for drilling earth formations



Oct. 25, 1966 J. w. GRAHAM ETAL 3,

BIT FOR DRILLING EARTH FORMATIONS 2 Sheets-Sheet 1 Original Filed May13, 1959 INVENTORS. JOHN W. GRAHAM, LEON H. ROBINSON,JR.,

TTO

Oct. 25, 1966 J. w. GRAHAM ETAL 3,

BIT FOR DRILLING EARTH FORMATIONS 2 Sheets-Sheet 2 Original Filed May15, 1959 DIAMONDS 45 INVENTORS- JOHN W. GRAHAMI BY LEON H. ROBINSON ATTOUnited States Patent M 3,280,926 BIT FOR DRILLING EARTH FORMATIONS JohnW. Graham, Bellaire, and Leon H. Robinson, In, Houston, Tex., assignors,by mesne assignments, to Esso Production Research Company, Houston,Tex., a corporation of Delaware Application May 25, 1962, Ser. No.197,674, now Patent No. 3,163,242, dated Dec. 29, 1964, which is adivision of application Ser. No. 812,864, May 13, 1959, now Patent No.3,078,934. Divided and this application Feb. 24, 1964, Ser. No. 346,660

4 Claims. (Cl. 175330) The present invention is directed to a drill bit.More particularly, the invention is concerned with drilling a Well inwhich increased drilling rates are obtained. In its more specificaspects, the invention is concerned with an improved drill bit andmethod for a drilling well.

This application is a division of Serial No. 197,674, file-d May 25,1962, for John W. Graham and Leon H. Robinson, Jr., entitled Drill Bit,which in turn is a division of Serial No. 812,864, filed May 13, 1959,now

Patent No. 3,078,934, for John W. Graham and Leon H.

Robinson, Jr., entitled Drilling of Earth Forma-tions by Extrusion.

The present invention may be briefly described as a drill bit fordrilling a well in which a body mentber attached to a hollow drillstring has a drill member mounted on the body member for contactingearth formations. The drill member is formed to provide a plurality ofopen-ended passageways with at least one of the ends of each of thepassageways being formed to contact the earth formation peripherally indrilling of the well. Each of the passageways discharge into the well orinto the circulating drilling fluid which in turn is discharged into thewell whereby a portion of the earth formation is extruded through eachof the passageways in contact with the earth formation.

The drill member may be rotatably or rigidly mounted on the body memberand the drill member may be substantially a sphere or the drill membermay be a toothed roller with the passageways being formed in the teethor in a band in the outer edge of the tooth roller. The drill member maybe cone-shaped and the band may be on the base of the cone with thepassageways discharging below the band adjacent the teeth.

In drilling of wells, it is belived that the stress distribution withinthe rock is in part responsible for the slow drilling which isfrequently encountered. The rock may be tectonically relaxed in aparticular area of interest and, thus, the principal stresses within therock may be equal. However, if a hole is drilled through this area, thehole will create discontinuities and stresses, particularly at or nearthe bottom of the hole. For example, the outer edge of the borehole maybe under considerable compression because of the discontinuity caused bythe presence of the hole. Moreover, the greater the sharpness of thecorners (that is, the smaller the radius of the curvature), the greaterwill be the compressional stresses around the periphery of the hole.Stresses that are superimposed over the stress of the rock are thosecreated by hydrostatic pressure of the fluid in the borehole, theoverburden pressure caused by the weight of the formation, and the fluidpressure in the pores of the formation.

In areas where the subsurface rock fails malleably while drilling, anideal situation would make full use of the compressional stressesexisting at the bottom of the borehole. The drill bits employed in theart, however, do not take advantage of the stresses created by theborehole. It is, therefore, a feature of the present invention not onlyto exploit the stresses in existence, which will increase drillingrates. This is done by im- 3,280,926 Patented Oct. 25, 1966 but also togenerate additional stresses within the rock posing pressure on theearth formation pierced by the well at a plurality of spaced-apartpoints and extruding a portion of the formation from the bottom of thewell through the drill bit at a plurality of points within the peripheryof each of said plurality of points where the pressure is imposed.

This may be accomplished in a number of ways and, therefore, theinvention will be further described by reference to the drawings inwhich:

FIG. 1 is a sectional view of a bit tooth of a preferred embodiment ofthe present invention in contact with the bottom of a well;

FIG. 2 is a view of a modified drill bit in accordance with FIG. 1 ofthe present invention;

FIG. 2a is a fragmentary sectional view of the band of -FIG. 2;

'FIG. 3 is a further modification of the device of FIG. 2;

FIG. 3a is a sectional view of the elephant foot teeth of the device ofFIG. 3;

FIG. 4 illustrates a bit embodying the present invention;

FIG. 4a is a partial sectional view of FIG. 4;

FIG. 5 is a still further modification of the present invention; and aFIG. 5a is a bottom view of the device of FIG. 5.

Referring now to the drawing and particularly to FIG. 1, numeral 11designates the wall of a well drilled from the earths surface, notshown, and having a drill bit 12 carried on the lower end of a drillstn'ng, not shown, contacting the bottom 13 of the well with the tooth'14, which is provided with a tapered passageway 15 drilled through thetooth and opening into the well. These holes 15 may be from A3 to inchin diameter and may be arranged in the outer ring of teeth on each coneof a hard rock bit. When the tooth 14 contacts the formation and beginsto destroy the formation immediately below the bit 12, a portion of theformation is extruded into and ultimately passes through the passageway15 and discharges into the annulus 16 and then is removed from the wellwith the drilling fluid. As the tooth continues its journey, theextruded rock removed from the region B in the bottom of the well 13leaves a small hole below the zone of the destruction normally producedby the bit. This small hole produces stresses in the rock because of thediscontinuity of the bottom of the hole just as the discontinuityproduced by the borehole 11 induces compressional stresses around theperiphery of the borehole. Accordingly, destruction of the rock isincreased immediately surrounding the region B from which the rock isextruded, and, therefore, increased drilling rates are obtained.

In ordinary drilling operations, the solid bit teeth of conventionalbits cause regions A surrounding each tooth to fail by brittleness and,thus, small rock chips are created therein. No advantage is taken of thetremendous malleability existing immediately below each bit tooth. Theimproved bit and method of drilling with the passageway 15 in the bittooth 14 allows the rock to deform malleably through the tooth and,hence, is removed permanently from region B.

In FIG. 2, a modified bit 20 having a body 21 has a plurality of rollercutters 22 rotatably mounted on the body 21. In the improved bit 20 ofthe present invention, the cone-shaped roller 22 has a band 23 on theouter edge of each of thecones provided with a plurality of open-endedpassageways 24 tapering to a larger opening 25 immediately above theteeth 26 which are adjacent the apex of the cone. The holes 24 aresuitably placed in the center of the band and are tapered with thesmaller opening on the side of the band which contacts the bottomplurality of open-ended passageways 28. These teeth have a large bearingsurface and may be provided with a plurality of the tapered holes 28' asshown in FIG. 3a.

As shown in the drawing, the bearing is flat. As a modification of FIG.3, all of theteeth of the device of FIG. 3 may be of the elephant foottype.

As a further modification of the present invention, a body member 30 inFIG. 4, which suitably may be a drill collar attached to a drill string,is provided with a plurality of mud ports 31 for circulation of drillfluid and has a spindle 32 rigidly attached thereto on which isrotatably mounted a sphere 33 provided with a plurality of openendedpassageways 34 which are" tapered. As shown in FIG. 4a, the spindle 32is arranged in a sleeve bear-ing 3311 which makes a press fit in arecess in sphere 33 designed to receive the sleeve bearing 33a. Splitrings 35 are urged into split ring groove 32a on spindle 32 and intosplit ring groove 36 in sleeve bearing 33a, thus making a connectionbetween the sphere 33 and spindle 32. In drilling with the device ofFIG. 4 and FIG. 4a, the sphere 33 by virtue of its eccentric arrangementon the spindle 32 re volves off-center around the spindle 32 and therock is extruded into and passes through the passageways 34 and carriedup the hole with the drilling fluid. Also, rotation of the sphere 33causes abrasion of th bottom and wall of the hole, thus advancing thebit through the formation being drilled.

As a still further modification of the present invention, as shown inFIGS. and 5a, a body member such as 40 provided with mud ports 41 hasformed thereon a plurality of spikes 42, each of which has an open-endedpassageway 43 terminating at the bottom of the spike and dischargingwithin the cavity 44 which, in turn, discharges into the well throughmud ports 41. The spikes 42 have fiat bottom faces, as shown in FIGS. 5and 5a, and are mounted on body member 40 such that the flat bottomfaces are all in the same plane. The spikes 42 may be constructed .oftungsten carbide and may also have diamonds 45 mounted on the peripheryof the spikes 42 such that when the improved device 40 is rotated andreciprocated, a scratching or churning action accompanies the extrusionaction of the rock through the passageways 43-. The spikes 42 incontacting the bottom of the well form channels with concentric shellsof formation material between the channels. The shells are crushed asthe bit penetrates the formation and the crushed, as well as theextruded, material is carried upwardly with the drilling fluid. Thecavity 44 communicates fluidly with the drill string and the extrudedmaterial passes through the passageways 43 into the cavity 44 and thencedownwardly with the drilling fluid through ports 41 and upwardlytherewith to the earths surfacebe-tween the drill string and the wall ofthe well.

The present invention is quite advantageous and useful in that byimposing pressure on the rock, it becomes malleable and is caused to beextruded, creating additional stresses within the rock being drilled andthus contributing to improved drilling operations.

The invention will be further described by reference to the followingoperation in which water-saturated carthage marble was subjected to aconfining pressure of 10,000 p.s.i. A tubular member having a inchopening next to its face compressed the confined marble about 0.25 inch.The marble yielded and deformed malleably which caused it to extrudeinto the opening.

-In practicing the invention, the malleable state occurs when theconfining pressure is greater than the pore pressure of the rock by anamount in the range from about 2500 to about 5000 p.s.i., which mayoccur in wells at depths from about 5000 to about 10,000 feet.

The nature .and objects of the present invention having been completelydescribed and illustrated, what we wish to claim as new and useful andsecure by Letters Patent is:

1. A drill bit adapted to be connected to a hollow drill string fordrilling a well which comprises a body member having a cavity thereinadapted to communicate fluidly with said drill string and provided withports for discharge of drilling fluid, a plurality of tungsten carbidespikes rigidly mounted on said body member for contacting an earthformation having diamonds mounted on the periphery of the free endthereof, said spike-s being formed to provide a plurality of open-endedpassageways, the free end of each of said spikesbeing adapted to contactsaid earth formation peripherally of each of said passageways indrilling of said well and the other end of each of said passagewaysdischarging into said cavity, said spikes having fiat bottom faces onthe free end thereof and being mounted on said body member such that theflat bottom faces are all in the same plane, whereby a portion of saidearth formation is extruded int-0 and passes through each of saidpassageways in contact with said earth formation into said cavity and isdischarged through said ports with the drilling fluid.

2. A drill bit adapted to be connected to a hollow drill string fordrilling a well which comprises a body member having a cavity thereinadapted to communicate fluidly with said drill string and provided withports for discharge of drilling fluid, a plurality of outwardlyextending tungsten carbide members mounted on said body member forcontacting an earth formation having diamonds mounted on the peripheryof the free end thereof, said outwardly extending members being formedto provide a plurality of open-ended passageways, the free end of eachof said outwardly extending members being adapted to'contact said earthformation peripherally of eachof said passageways in drilling of saidwell and the other end of each of said passageways discharging into saidcavity, said outwardly extending members having flat bottom faces on thefree end thereof and being mounted on said body member such that thefiat bottom faces are all in the same plane, whereby a portion of saidearth formation is extruded into and passes through each of saidpassageways in contact with said earth formation into said cavity and isdischarged [through said ports with the drilling fluid.

3. A drill bit in accordance with claim 2 in which the outwardlyextending members are tubular.

4. A drill bit in accordance with claim 1 in which the spikes aretubular.

FOREIGN PATENTS 717,706 11/1954 Great Britain.

i CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, Examiner. N. C. BYERS, Assistant Examiner.

1. A DRILL BIT ADAPTED TO BE CONNECTED TO A HOLLOW DRILL STRING FORDRILLING A WELL WHICH COMPRISES A BODY MEMBER HAVING A CAVITY THEREINADAPTED TO COMMUNICATE FLUIDLY WITH SAID DRILL STRING AND PROVIDED WITHPORTS FOR DISCHARGE OF DRILLING FLUID, A PLURALITY OF TUNGSTEN CARBIDESPIKES RIGIDLY MOUNTED ON SAID BODY MEMBER FOR CONTACTING AN EARTHFORMATION HAVING DIAMONDS MOUNTED ON THE PERIPHERY OF THE FREE ENDTHEREOF, SAID SPIKES BEING FORMED TO PROVIDE A PLURALITY OF OPEN-ENDEDPASSAGEWAYS, THE FREE END OF EACH OF SAID SPIKES BEING ADAPTED TOCONTACT SAID EARTH FORMATION PERIPHERALLY OF EACH OF SAID PASSAGEWAYS INDRILLING SAID WELL AND THE OTHER END OF EACH OF SAID PASSAGEWAYSDISCHARGING INTO SAID CAVITY, SAID SPIKES HAVING FLAT BOTTOM FACES ONTHE FREE END THEREOF AND BIENG MOUNTED ON SAID BODY MEMBER SUCH THAT THEFLAT BOTTOM FACES ARE ALL IN THE SAME PLANE, WHEREBY A PORTION OF SAIDEARTH FORMATION IS EXTRUDED INTO AND PASSES THROUGH EACH OF SAIDPASSAGEWAYS IN CONTACT WITH SAID EARTH FORMATION INTO SAID CAVITY AND ISDISCHARGED THROUGH SAID PORTS WITH THE DRILLING FLUID.